Annals of botany最新文献

Background and aims: Developmental genetic studies in model species have unveiled genes that modulate organ size. The roles of homologs of these genes in angiosperms with complex ontogenies such as the "flower shoots" of Cactaceae have not yet been analyzed. Here we present histological, cellular, and transcriptome analysis from flower buds in two developmental stages for two cacti species with contrasting flowers: Disocactus speciosus and D. eichlamii.

Methods: Analyses of cell area, cell number, and overall tepal size from floral buds were performed to determine if differential cell proliferation and expansion occurred. We also performed transcriptome analyses derived from size 1 and 2 floral buds, differential gene expression analysis, followed by KEGG enrichment.

Key results: Comparative histological and cellular analyses in Disocactus tepals indicate that while size 1 cells are similar in size in both species, a prolonged expansion phase takes place in D. speciosus. Transcriptome analyses suggest similar overall expression patterns per size, but differential expression of genes related to tepal growth were documented like BIG PETALp (BPp), down-regulated in size 1 vs size 2 in D. eichlamii. In this species we found BIG BROTHER (BB) up-regulated in size 1 vs size 2. In contrast, in D. speciosus, we found two copies of BB, one copy up-regulated and the other down-regulated, as well as NAC100 which could be related with the final size of the flower in this species.

Conclusions: This study integrates cellular and molecular data related with the development of differential organ size in Cactaceae. We found that a prolonged period of cell proliferation and expansion in D. speciosus tepals in contrast with D. eichlamii tepals seems to correlate with its final size, while transcriptome analyses point to several DEGs that should be further investigated through gene expression analyses as well as other reverse genetics approaches.

Background and aims: Leaf size and the total number of leaves per shoot (NT) reflect plant resource allocation strategies. Although studies often focus on single leaves, the leaf scaling relationships at the whole-shoot level are less known, especially in species with vertical leaf arrangements. This study investigates how total leaf area (AT), total leaf dry mass per shoot (MT), and NT scale with each other in the bamboo Semiarundinaria densiflora, which has a near-vertical foliage structure.

Methods: We sampled 121 culms with over 9200 leaves and measured AT, MT, NT, and maximum individual leaf area per culm (Amax). The scaling relationships were examined using reduced major axis regression protocols. The distribution of NT was modeled with a negative binomial distribution.

Key results: N T fit a negative binomial distribution. AT and MT scaled allometrically with NT, with scaling exponents > 1. AT scaled isometrically with both the product of NT and Amax, and with MT.

Conclusions: The vertical foliage in S. densiflora leads to self-shading, promoting larger, thinner basipetal shade leaves. This results in a disproportionate increase in AT with NT and an isometric AT vs. MT relationship, which contrasts with the "diminishing returns" pattern seen in individual leaves. Canopy architecture therefore is key in shaping biomass allocation.

Background: WRKY transcription factors are a plant-specific family of key regulators involved in floral pigmentation, scent biosynthesis, and stress responses, and thus provide a molecular entry point for trait improvement. However, WRKY studies in Oleaceae still largely rely on single reference genomes, which incompletely capture structural variations and accession-level functional diversity.

Scope: This review summarizes recent progress in WRKY research across ornamental plants, with emphasis on the current status and resource limitations in Oleaceae. We highlight how pangenomic frameworks can uncover presence-absence variations (PAVs), copy-number variations (CNVs) and other structural variants that shape WRKY repertoires. We discuss how these resources enable the delineation of core versus variable WRKY members and support variant-to-trait hypotheses for key ornamental traits. We further propose a pangenome-driven strategy to guide the prioritization of functional WRKY candidates underlying floral coloration and scent formation, integrating comparative genomics, structural-variant profiling and multi-omics evidence.

Conclusions: Incorporating pangenomics into WRKY family analyses is expected to move Oleaceae research beyond single-reference catalogues towards trait-oriented gene discovery. A pangenome-enabled workflow significantly enhances the resolution of WRKY diversity and variant-trait hypotheses, thereby laying a foundation for functional validation and molecular breeding of cultivars that harmonize superior fragrance and coloration with enhanced environmental stress resilience.

Background and aims: In savanna ecosystems, water availability and fire are interconnected, shaping plant structure and diversity. In Cerrado, factors such as water seasonality and fire-related cues (e.g., smoke) interact to influence recruitment. This study investigated the germinative and post-germinative responses of Cerrado ground-layer species to a gradient of water potential reduction, both independently and in combination with smoke water (SW). It assessed the effects of smoke and water deficit on treatment (WDT) and post-water deficit recovery (WDR), exploring the potential protective role of smoke under these conditions.

Methods: Different concentrations of polyethylene glycol 6000, both alone and in combination with 10 and 25 mL L-1 of SW, were used to assess the germination and seedling growth responses of 15 Cerrado ground-layer species at 25°C. After WDT, species were subjected to the WDR (using only deionized water) to evaluate recovery capacity. Effect sizes were used to evaluate species' responses to the treatments and whether these responses were associated with growth forms (i.e., shrubs and herbs).

Key results: Reduced water potential was the primary factor negatively impacting germination and post-germination responses. While species-specific, SW had a protective effect on germination and seedling growth under moderate water deficit. Tolerance to water deficit was more evident in shrub species, whereas positive responses to SW were more common in herbaceous species. During WDR, most species either recovered from WDT and germinated or maintained seed viability. Herbaceous species showed a stronger recovery, with germination reaching control levels.

Conclusions: Both water potential reduction and SW influence the germination and seedlings' growth of Cerrado ground-layer species and growth forms. Smoke can alleviate stress induced by water deficit, with species showing tolerance without loss of seed viability, suspending germination under stress but retaining their ability to recover.

Background and aims: Seed germination is highly temperature sensitive, and increasing global temperatures due to climate change are likely to have a strong effect on agriculture. Improved utilisation of indigenous, arid-resilient crops like fonio (Digitaria exilis) are a commonly proposed solution to improving food security in West Africa. This study develops knowledge of fonio germination requirements and relates them to future predicted climate conditions.

Methods: We use an interdisciplinary methodology, integrating extensive laboratory-based seed germination experiments under a range of temperatures, with niche suitability and future climate modelling, to investigate trends for how cultivation of fonio may be impacted by climate change.

Key results: By analysing 37 seed accessions from Guinea, Togo, Mali, and Burkina Faso, we estimated the ceiling temperature for germination of this species to be 43°C (SD=±1.6), with an optimum temperature of 36°C (SD=±2.2) - as also noted from phenotypic observations on seedlings. There is no obvious difference in response by accessions originating from either hotter or cooler climates. By comparing these temperature thresholds to future climate predictions, tested alongside suitability modelling, we see a decline of 7.9-10.45% in the future suitable area for fonio cultivation, depending on the prediction method, especially affecting Senegal, Mali, and Burkina Faso. Newly suitable area is predicted to increase in Guinea, Ghana, Cote d'Ivoire, and Nigeria by 5.5%.

Conclusions: Our findings provide valuable insight into the physiology and thermal tolerance of fonio seeds, and identify particularly vulnerable agricultural regions in West Africa which will require additional support. This should include developing future dryland agriculture policies, livelihood projects, and resilient crop varieties.

Background and aims: Butia capitata diaspores require years to germinate due to dormancy, determined by the association between an embryo with low growth potential and restrictive sites of a seminal and pericarpal nature. The species is endemic to the highly seasonal environment of the Cerrado biome. We evaluated the role of temperature in controlling the force balance of the micropylar region, aiming to characterize the relationship between overcoming dormancy and adaptation of germination to seasonality.

Methods: A wide range of thermal regimes was applied to isolated embryos, isolated seeds and diaspores (i.e. pyrenes = seeds enclosed by the endocarp). Pyrenes were subjected to thermal cycles: 11 alternating temperature regimes (90 days) + 30 °C (30 days), in association with moisture conditions (dry and moist) in freshly harvested pyrenes and pyrenes subjected to conditioning (1-year storage, burial in the greenhouse, burial in the natural environment and after-ripening), totaling 168 treatments. In each thermal cycle, germination and the force balance in the micropylar region (embryo growth potential vs. the resistance of adjacent tissues) were evaluated.

Key results: Thermal variation differentially affects the interaction sites of the micropylar region, which favors the maintenance of dormancy. The heterogeneity of diaspores makes the overcoming of dormancy dependent on thermal cycles, which results in germination being spread out over years. 35/20 °C regime contributes to overcoming dormancy (germination rates of 92%), at the end of the second thermal cycle.

Conclusions: Temperature plays a crucial role in overcoming seed dormancy. The thermal regime occurring at the transition between the dry and rainy seasons promotes dormancy overcoming, synchronizing germination with ecological windows of opportunity for seedling establishment, during the wet season. These results broaden our understanding of the mechanisms involved in overcoming seed dormancy in palms and other species with woody, indehiscent endocarps, especially those from seasonal environments.

Cardamine hupingshanensis is a selenium (Se) hyperaccumulating plant discovered in 2008 in China. This comprehensive review summarizes the state-of-the-art progress on the molecular mechanisms underlying Se hyperaccumulation in C. hupingshanensis. The direct mechanisms encompass the key genes involved in the Se accumulation, localization and transformation processes in the plant. Homocysteine S-methyltransferase (HMT) and methionine S-methyltransferase (MMT) may contribute to Se hyperaccumulation in C. hupingshanensis, supported by the detection of selenolanthionine in the water extraction fraction, and selenocystine and selenomethylcysteine in the proteolytic hydrolysate fraction. Indirect mechanisms, such as structural adaptations, sequestration/transportation, sulphur conservation, oxidative stress control, protein degradation and interactions with rhizosphere/endophytic microbiota, may also contribute to its Se hyperaccumulation. This review also explores the applications of Se biofortification and phytoremediation, highlighting the potential of C. hupingshanensis in enhancing Se content in crops and remediating Se-contaminated environments. Further investigation is needed into the challenges related to C. hupingshanensis, focusing on the pathways and processes of Se accumulation and transport within the rhizosphere soil-plant-air system, comparative studies that have used a multi-omics strategy to delve deeper into the molecular mechanisms of Se hyperaccumulation under various Se speciation treatments, the role of core microbiota, potential applications in food processing and agriculture, and the synergistic remediation of Se and other heavy metal contaminants.

Background and aims: In our previous study, interspecific grafting of Populus cathayana (C) onto Populus deltoides (D) significantly improved the drought tolerance in grafted plants. However, whether this advantage could be maintained under salt stress conditions and the relative underlying mechanism are unclear.

Methods: Physiological, long non-coding RNA (lncRNA) sequencing and metabolic analyses were performed to illuminate the mechanism governing the different responses to salt stress between C/D (C grafted onto D) and D/C (D grafted onto C) plants.

Key results: Salt stress reduced the growth and biomass of all the grafted plants, with C/D plants showing stronger salt tolerance than D/C plants, as evidenced by their greater biomass production and sugar content, less leaf cell damage and better ion homeostasis. More lncRNAs, mRNAs and metabolites related to carbohydrate metabolism were detected in D/C than in C/D plants. Genes related to metabolism of structural and non-structural carbohydrates were respectively up- and down-regulated in C/D and D/C plants, and the changes of citramalic acid, sorbitol and pyruvic acid contents were strongly supported by their different carbohydrate metabolisms. In addition, the lncRNAs MSTRG.102 and MSTRG.4684, as well as their target genes involved in carbohydrate metabolism, were less significantly down-regulated in C/D than in D/C plants. Furthermore, correlation analysis revealed that MSTRG.7877 and MSTRG.20540 might be key lncRNAs in the grafted plants in response to salt stress.

Conclusions: Our study demonstrates that by affecting the accumulation and metabolism of carbohydrates, different expression and content of multiple lncRNAs, mRNAs and metabolites, associated with structural and non-structural carbohydrates, led to different growth and salt tolerance between C/D and D/C plants. The improved growth and salt tolerance in C/D plants was closely associated with the altered accumulation and metabolism of structural and non-structural carbohydrates.